linux/arch
Laurent Dufour c1d0da8335 mm: replace memmap_context by meminit_context
Patch series "mm: fix memory to node bad links in sysfs", v3.

Sometimes, firmware may expose interleaved memory layout like this:

 Early memory node ranges
   node   1: [mem 0x0000000000000000-0x000000011fffffff]
   node   2: [mem 0x0000000120000000-0x000000014fffffff]
   node   1: [mem 0x0000000150000000-0x00000001ffffffff]
   node   0: [mem 0x0000000200000000-0x000000048fffffff]
   node   2: [mem 0x0000000490000000-0x00000007ffffffff]

In that case, we can see memory blocks assigned to multiple nodes in
sysfs:

  $ ls -l /sys/devices/system/memory/memory21
  total 0
  lrwxrwxrwx 1 root root     0 Aug 24 05:27 node1 -> ../../node/node1
  lrwxrwxrwx 1 root root     0 Aug 24 05:27 node2 -> ../../node/node2
  -rw-r--r-- 1 root root 65536 Aug 24 05:27 online
  -r--r--r-- 1 root root 65536 Aug 24 05:27 phys_device
  -r--r--r-- 1 root root 65536 Aug 24 05:27 phys_index
  drwxr-xr-x 2 root root     0 Aug 24 05:27 power
  -r--r--r-- 1 root root 65536 Aug 24 05:27 removable
  -rw-r--r-- 1 root root 65536 Aug 24 05:27 state
  lrwxrwxrwx 1 root root     0 Aug 24 05:25 subsystem -> ../../../../bus/memory
  -rw-r--r-- 1 root root 65536 Aug 24 05:25 uevent
  -r--r--r-- 1 root root 65536 Aug 24 05:27 valid_zones

The same applies in the node's directory with a memory21 link in both
the node1 and node2's directory.

This is wrong but doesn't prevent the system to run.  However when
later, one of these memory blocks is hot-unplugged and then hot-plugged,
the system is detecting an inconsistency in the sysfs layout and a
BUG_ON() is raised:

  kernel BUG at /Users/laurent/src/linux-ppc/mm/memory_hotplug.c:1084!
  LE PAGE_SIZE=64K MMU=Hash SMP NR_CPUS=2048 NUMA pSeries
  Modules linked in: rpadlpar_io rpaphp pseries_rng rng_core vmx_crypto gf128mul binfmt_misc ip_tables x_tables xfs libcrc32c crc32c_vpmsum autofs4
  CPU: 8 PID: 10256 Comm: drmgr Not tainted 5.9.0-rc1+ #25
  Call Trace:
    add_memory_resource+0x23c/0x340 (unreliable)
    __add_memory+0x5c/0xf0
    dlpar_add_lmb+0x1b4/0x500
    dlpar_memory+0x1f8/0xb80
    handle_dlpar_errorlog+0xc0/0x190
    dlpar_store+0x198/0x4a0
    kobj_attr_store+0x30/0x50
    sysfs_kf_write+0x64/0x90
    kernfs_fop_write+0x1b0/0x290
    vfs_write+0xe8/0x290
    ksys_write+0xdc/0x130
    system_call_exception+0x160/0x270
    system_call_common+0xf0/0x27c

This has been seen on PowerPC LPAR.

The root cause of this issue is that when node's memory is registered,
the range used can overlap another node's range, thus the memory block
is registered to multiple nodes in sysfs.

There are two issues here:

 (a) The sysfs memory and node's layouts are broken due to these
     multiple links

 (b) The link errors in link_mem_sections() should not lead to a system
     panic.

To address (a) register_mem_sect_under_node should not rely on the
system state to detect whether the link operation is triggered by a hot
plug operation or not.  This is addressed by the patches 1 and 2 of this
series.

Issue (b) will be addressed separately.

This patch (of 2):

The memmap_context enum is used to detect whether a memory operation is
due to a hot-add operation or happening at boot time.

Make it general to the hotplug operation and rename it as
meminit_context.

There is no functional change introduced by this patch

Suggested-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Laurent Dufour <ldufour@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Oscar Salvador <osalvador@suse.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J . Wysocki" <rafael@kernel.org>
Cc: Nathan Lynch <nathanl@linux.ibm.com>
Cc: Scott Cheloha <cheloha@linux.ibm.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: <stable@vger.kernel.org>
Link: https://lkml.kernel.org/r/20200915094143.79181-1-ldufour@linux.ibm.com
Link: https://lkml.kernel.org/r/20200915132624.9723-1-ldufour@linux.ibm.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2020-09-26 10:33:57 -07:00
..
alpha treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
arc ARC fixes for 5.9-rc4 2020-09-05 13:46:14 -07:00
arm Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2020-09-22 14:43:50 -07:00
arm64 ARM: 2020-09-21 08:53:48 -07:00
c6x treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
csky treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
h8300 treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
hexagon treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
ia64 mm: replace memmap_context by meminit_context 2020-09-26 10:33:57 -07:00
m68k treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
microblaze microblaze: fix min_low_pfn/max_low_pfn build errors 2020-08-31 19:52:50 +03:00
mips - fixed FP register access on Loongsoon-3 2020-09-25 15:24:04 -07:00
nds32 A set of fixes for lockdep, tracing and RCU: 2020-08-30 11:43:50 -07:00
nios2 mm/nios2: use general page fault accounting 2020-08-12 10:58:03 -07:00
openrisc OpenRISC fixes for 5.9-rc4 2020-09-12 13:03:49 -07:00
parisc treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
powerpc powerpc fixes for 5.9 #5 2020-09-18 11:48:25 -07:00
riscv RISC-V Fixes for 5.9-rc6 (or shortly after) 2020-09-20 10:51:11 -07:00
s390 mm/gup: fix gup_fast with dynamic page table folding 2020-09-26 10:33:57 -07:00
sh sh: fix syscall tracing 2020-09-13 21:22:55 -04:00
sparc treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
um treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
x86 arch/x86/lib/usercopy_64.c: fix __copy_user_flushcache() cache writeback 2020-09-26 10:33:57 -07:00
xtensa treewide: Use fallthrough pseudo-keyword 2020-08-23 17:36:59 -05:00
.gitignore
Kconfig A set oftimekeeping/VDSO updates: 2020-08-14 14:26:08 -07:00